1. Field of the Invention
The present invention relates to a multifunctional-type backlight unit which is configured to give an optical communication function and a solar light collection function to a backlight unit for illumination of a display, and an information device using the multifunction-type backlight unit.
2. Description of Related Art
In general, a liquid crystal panel combined with a backlight unit utilizing surface emission from a light guiding plate comprised in the backlight unit has been used as a display for a mobile phone, a personal computer, or the like. Various improvements in the backlight unit have been made.
An improved light guiding plate to accomplish uniform brightness of surface emission and a backlight unit using such a light guiding plate are already known (see, for reference, Japanese Patent Laid-Open No. 2001-210120, claims, FIG. 1).
FIG. 6A illustrates a conventional backlight unit disclosed in Japanese Patent Laid-Open No. 2001-210120.
The backlight unit includes a light guiding plate 50. The light guiding plate 50 has a generally rectangular shape and includes an incident surface 51 for light, a bottom surface 52 and an exit surface 53 for light. A plurality of grooves 54, each of which has a triangular shape in section and extends in parallel with a long side of the incident surface 51 to form a triangular prism shaoe are formed in the bottom surface 52 at predetermined intervals. A light source 55 is disposed to face the incident surface 51, and the light source 55 is covered by a light collecting plate 56 so that light emitted from the light source 55 enters the incident surface 51. In addition, a diffusing and reflecting sheet 57 is provided to face the bottom surface 52 of the light guiding plate 50.
Here, the light emitted from the light source 55 passes through the incident surface 51 and enters the light guiding plate 50 where it is reflected on the bottom surface 52 and the exit surface 53, travels in a direction (arrow A) away from the incident surface 51 in the light guiding plate 50, enters the grooves, and is refracted therein to be guided to the exit surface 53.
Next, a path of the light emitted from the light source 55 is described referring to FIG. 6B.
The light emitted from the light source 55 enters the light guiding plate 50 through the incident surface 51, travels in the direction of arrow A while undergoing repeated reflection on the bottom surface 52 and the exit surface 53, and enters the grooves 54a, 54b, 54d and 54e. The light 58a entering the groove 54a, the light 58b entering the groove 54b, the light 58d entering the groove 54d, and the light 58e entering the groove 54e are reflected on the respective grooves and guided to the exit surface 53.
Here, the grooves 54a to 54e formed in the bottom surface 52 are formed so that each of the grooves has a depth increasing in sequence from the groove 54a disposed close to the incident surface 51 to the groove 54e disposed furthest from the incident surface 51, so that, even if the intensity of the light decreases at grooves positioning away from the incident surface 51, increasing proportion of light received by the grooves positioning away from the incident surface 51 is achieved, thus allowing a uniform and intensified light to be guided to the exit surface.
Moreover, a typical information equipment such as a conventional mobile phone, laptop computer or the like provided with a data communication device has been developed, and a mobile phone including an infrared communication device as a data communication system has also been developed (see, for reference, Japanese Patent Laid-Open No. 2004-294310, claims, FIG. 1).
FIG. 7 illustrates a mobile phone including a conventional communication device and a communication system, as disclosed in Japanese Patent Laid-Open No. 2004-294310.
The mobile phone 60 includes an infrared transmitting and receiving section 62 allowing function other than a normal communication function using an antenna 61. A car navigation device 63 includes a display 64 and an infrared transmitting and receiving section 65. Consequently, a communication system using infrared rays 66 may be structured between the infrared transmitting and receiving section 62 of the mobile phone 60 and the infrared transmitting and receiving section 65 of the car navigation device 63.
Here, the mobile phone 60 stores phone number data of a destination in an inner memory thereof and transmits the phone number data to the car navigation device 63 by infrared rays 66 if required. If the received phone number data is set in the car navigation device 63 as the destination, the car navigation device 63 can guide the user to the destination.
With the above-mentioned configuration, when the user rides in a vehicle, the destination can be automatically set on the car navigation device simply by placing the mobile phone in the vicinity of the car navigation device, that can eliminate a complicated operation.
The backlight unit as disclosed in Japanese Patent Laid-Open No. 2001-210120 needs a relatively large space for installation, compared with other structural elements of an information device in which the backlight unit is installed, though the backlight unit has a single function for illuminating a liquid crystal panel or the like as a backlight.
In particular, in recent years, a mobile information device represented by a mobile phone, notebook computer or the like has been provided with advanced and sophisticated features. As a result, there is strong demand for compactness and light weigh.
To satisfy the requirement mentioned above, for example, a multifunctional-type part which can provide for a plurality of functions with a shared use of one installed component, that cannot be provided by a conventional backlight unit.
Usually, the mobile phone or the like have a communication device using infrared, as disclosed in Japanese Patent Laid-Open No. 2004-294310, utilizing an infrared communication device. The disclosed infrared communication device is limited to low power transmission, in view of the need to protect the eyes of a user or persons in the vicinity. As a result, the infrared communication device has problems of limited communication distance, resulting in communication failure of long distance. Also, there is a problem of low communication speed.
In recent years, a wireless communication device using a radio wave such as Bluetooth has been used in the field, as a wireless communication technology between information devices. However, it is difficult to achieve a wide generalization of the technology, because there are strict limitations on the output and also frequencies of the electric wave may influence on the human body, medical devices or the like. Furthermore, there are restrictions on the method of radio wave production or the like. In addition, because the number of parts assembled in the information device increases, when it is structured to contain the infrared communication device or the wireless communication device using radio waves. Consequently it may be difficult to achieve miniaturization of the information device and cost reduction.
FIG. 8 illustrates one example of a conventional charging system using a solar battery.
Reference number 43 shows a solar battery, 44 a transparent cover to protect the solar battery 43, 45 incident light entering the solar battery 43.
Here, because the incident light 45 enters the solar battery 43 in a generally perpendicular direction to the solar battery, it is required to broaden the receiving area of the solar battery 43 to obtain a large electromotive force, resulting in cost increase and sufficient space for the broadened receiving area of the solar battery.